The present invention is generally directed to a contact-type slip ring system that is utilized to transfer signals from a stationary reference frame to a moving reference frame and, more specifically, to a contact-type slip ring system that is suitable for high data rate communication.
Contact-type slip rings have been widely used to transmit signals between two frames that move in rotational relation to each other. Prior art slip rings of this nature have utilized precious alloy conductive probes to make contact with a rotating ring system. These probes have traditionally been constructed using round-wire, composite materials, button contacts or multi-filament conductive fiber brushes. The corresponding concentric contact rings of the slip ring are typically shaped to provide a cross-section shape appropriate for the sliding contact. Typical ring shapes have included V-grooves, U-grooves and flat rings. Similar schemes have been used with systems that exhibit translational motion rather than rotary motion.
When transmitting high-frequency signals through slip rings, a major limiting factor to the maximum transmission rate is distortion of the waveforms due to reflections from impedance discontinuities. Impedance discontinuities can occur throughout the slip ring wherever different forms of transmission lines interconnect and have different surge impedances. Significant impedance mismatches often occur where transmission lines interconnect a slip ring to an external interface, at the brush contact structures and where the transmission lines connect those brush contact structures to their external interfaces. Severe distortion to high-frequency signals can occur from either of those impedance mismatched transitions of the transmission lines. Further, severe distortion can also occur due to phase errors from multiple parallel brush connections.
The loss of energy through slip rings increases with frequency due to a variety of effects, such as multiple reflections from impedance mismatches, circuit resonance, distributed inductance and capacitance, dielectric losses and skin effect. High-frequency analog and digital communications across rotary interfaces have also been achieved or proposed by other techniques, such as fiber optic interfaces, capacitive coupling, inductive coupling and direct transmission of electromagnetic radiation across an intervening space. However, systems employing these techniques tend to be relatively expensive.
What is needed is a slip ring system that addresses the above-referenced problems, while providing a readily producible, economical slip ring system.